The immediate goal of the applicant is to devote 75% of his time during the five-year support period of this K02 award to the exploration of novel approaches to subcellular biology. The time off from teaching and service provided by the award would allow him to focus more intensely on the development of new strategies based on individual organelle analysis that would then be used to better understand disease and aging. These strategies are being developed as part of two ongoing R01 projects in his laboratory that investigate (i) the role of mitochondrial DNA (mtDNA) mutations in aging and age-related diseases, and (ii) subcellular drug metabolism. This award would also allow the candidate to devote more time to (i) integrating robotics, cybrid technology, and proteomics expertise into his laboratory; (ii) training scientists, (iii) establishing a solid network of collaborations, and (iv) providing cohesive leadership to a multi-disciplinary research team. In the research plan of this application, the candidate proposes to study the distributions of mtDNA mutations based on individual mitochondrion measurements. While the accumulation of these mutations has been implicated in the aging process and age-related diseases, the link between mutation levels and age-related phenotypes or disease symptoms is not known. The hypothesis of this application is that individual mitochondria contain both wild-type and mutated DNA, a condition known as heteroplasmy, which determines how mutations are distributed and propagated. Two models will be used to test this hypothesis: cybrid cell lines harboring large mtDNA deletions, and skeletal muscle tissue from aged Fisher 344 rats that is expected to have accumulated similar deletions with age. The three goals of the study are: (i) establish the existence of heteroplasmy within individual mitochondria, (ii) monitor changes in heteroplasmy following cybrid fusion, and (iii) measure heteroplasmy along skeletal muscle fibers. Since no technology exists to directly test this hypothesis, this application will require the further development of the applicant's strategies initially on based capillary electrophoresis with laser-induced fluorescence detection for characterizing mtDNA and peptide expression in individual organelles. Upon the completion of this K02 award, the applicant is expected to have provided the scientific community with new technologies and to be directing a widely recognized research program. [unreadable] [unreadable] [unreadable]